CN111234309A - Method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber - Google Patents
Method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber Download PDFInfo
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- CN111234309A CN111234309A CN202010211353.1A CN202010211353A CN111234309A CN 111234309 A CN111234309 A CN 111234309A CN 202010211353 A CN202010211353 A CN 202010211353A CN 111234309 A CN111234309 A CN 111234309A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
- C08J11/16—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with inorganic material
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2383/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
- C08J2383/04—Polysiloxanes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
Abstract
The invention discloses a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps: the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder; step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding solid acid and concentrated sulfuric acid, mixing and stirring to obtain pretreated waste silicon rubber powder; step three: and (3) heating the pretreated waste silicone rubber powder obtained in the step two until the material is liquefied, stirring and mixing for 5-10 min, reacting for 3-5 h under a vacuum condition, and collecting to obtain a cyclosiloxane monomer. The method can reduce equipment corrosion, greatly reduce calcium sulfate and residual sulfuric acid generated in the cracking slag, is beneficial to subsequent treatment and further recycling of the cracking slag, has the catalytic cracking efficiency equivalent to that of a concentrated sulfuric acid method, can recycle cyclosiloxane monomers accounting for 45-65% of the mass of the waste silicon rubber, and has strong industrial application prospect.
Description
Technical Field
The invention relates to the field of three-waste treatment methods, in particular to a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber.
Background
The silicone rubber is a special synthetic rubber which can keep the rubber elasticity for a long time within the range of-100 to 300 ℃, is nontoxic and tasteless, has good air permeability, has the outstanding characteristics of aging resistance and physiological inertia, and can not cause blood coagulation, and is widely applied to various industries and fields of electronics, architecture and building materials, textiles, light industry, medical treatment, machinery, transportation, plastic rubber and the like. Along with the increase of the demand of production and life for silicon rubber materials, the problem of recycling of waste silicon rubber is also important.
At present, the common methods for recovering cyclosiloxane monomers by using waste silicone rubber in China are a base catalytic cracking method, a thermal cracking method and an acid catalytic cracking method. The alkali catalytic cracking method has the advantages of small application range, difficult product utilization and poor safety, and local reaction over-severe is easy to occur in a reaction kettle to cause combustion and explosion accidents; the thermal cracking method has small reaction volume, more energy consumption, low recovery rate and lower safety; the acid catalytic cracking method has relatively high reaction safety and high recovery rate, and is widely applied in industry.
At present, a widely used method for recovering cyclosiloxane monomer by acid catalytic cracking of waste silicon rubber is a concentrated sulfuric acid cracking method, which has high cracking efficiency, but has the problems of strong corrosivity, high equipment replacement rate, difficult treatment of cracking residue, serious pollution and the like. The waste silicon rubber can be cracked by acid catalysis, the corrosivity is low, but the recovery rate and the recovery period of the whole cyclosiloxane monomer are greatly prolonged compared with the cracking by concentrated sulfuric acid due to insufficient reaction contact surface.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding solid acid and concentrated sulfuric acid, mixing and stirring to obtain pretreated waste silicon rubber powder;
step three: and (3) heating the pretreated waste silicone rubber powder obtained in the step two until the material is liquefied, stirring and mixing for 5-10 min, reacting for 3-5 h under a vacuum condition, and collecting to obtain a cyclosiloxane monomer.
As a preferable technical scheme, the particle size of the waste silicon rubber powder is less than 2 mm.
As a preferred technical scheme, the solid acid is Lewis acid and/or metal oxide solid super acid.
As a preferred technical scheme, the Lewis acid is selected from one or more of zinc chloride, aluminum chloride, zirconium chloride, titanium chloride and silicon chloride.
As a preferred technical scheme, the metal oxide solid super acid is a sulfate radical supported metal oxide solid super acid.
As a preferred technical scheme, the sulfate radical supported metal oxide solid super acid is selected from SO42-/ZrO2、SO42-/Fe2O3、SO42-/TiO2、SO42-/Al2O3、SO42-/SnO2、SO42-/Al2O3-ZrO2、SO42-/TiO2-ZrO2One or more combinations thereof.
As a preferable technical scheme, the mass fraction of the concentrated sulfuric acid is 98%.
As a preferable technical scheme, the weight ratio of the waste silicon rubber powder, the concentrated sulfuric acid and the solid acid is 1: (0.02-0.05): (0.08-0.15).
As a preferable technical scheme, the heating temperature of the pretreated waste silicon rubber powder in the third step is 140-200 ℃.
As a preferable technical proposal, the vacuum condition in the third step is below 0.08 MPa.
Has the advantages that: according to the method, the solid acid and concentrated sulfuric acid composite catalyst with a specific ratio is adopted to crack the waste silicon rubber, so that the corrosion of equipment can be reduced, the calcium sulfate and residual sulfuric acid generated in cracking slag are greatly reduced, the subsequent treatment and further recycling of the cracking slag are facilitated, the catalytic cracking efficiency is equivalent to that of a concentrated sulfuric acid method, the cyclosiloxane monomer with the mass being 45-65% of that of the waste silicon rubber can be recycled, and the industrial application prospect is strong.
Detailed Description
The technical features of the technical solutions provided by the present invention are further clearly and completely described below with reference to the specific embodiments, and the scope of protection is not limited thereto.
The words "preferred", "more preferred", and the like, in the present invention refer to embodiments of the invention that may provide certain benefits, under certain circumstances. However, other embodiments may be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.
In order to solve the technical problem, the invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding solid acid and concentrated sulfuric acid, mixing and stirring to obtain pretreated waste silicon rubber powder;
step three: and (3) heating the pretreated waste silicone rubber powder obtained in the step two until the material is liquefied, stirring and mixing for 5-10 min, reacting for 3-5 h under a vacuum condition, and collecting to obtain a cyclosiloxane monomer.
In a more preferred embodiment, the method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding solid acid and concentrated sulfuric acid, mixing and stirring to obtain pretreated waste silicon rubber powder;
step three: and (3) heating the pretreated waste silicone rubber powder obtained in the step two until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under a vacuum condition, and collecting to obtain a cyclosiloxane monomer.
< step one >
In a preferred embodiment, the particle size of the waste silicone rubber powder is less than or equal to 2 mm.
In a more preferred embodiment, the particle size of the waste silicone rubber powder is 2 mm.
The source of the waste silicone rubber is not particularly limited in the present invention, and various waste silicone rubbers well known to those skilled in the art can be used.
< step two >
(solid acid)
The solid acid is a solid acid having an acid site having catalytic activity on the surface.
In a preferred embodiment, the solid acid is a lewis acid and/or a metal oxide solid super acid.
Lewis acid
Lewis acids (electrophiles), also known as electrophiles, refer to substances (including ions, radicals or molecules) that can accept electron pairs.
In a preferred embodiment, the lewis acid is selected from one or more of zinc chloride, aluminum chloride, zirconium chloride, titanium chloride, and silicon chloride.
In a more preferred embodiment, the lewis acid is selected from one or more of zinc chloride, aluminum chloride, zirconium chloride in combination.
In a further preferred embodiment, the lewis acid is zinc chloride.
The zinc chloride of the invention, namely the anhydrous zinc chloride, has a CAS number of 7646-85-7.
Metal oxide solid super acid
The metal oxide solid super acid is a metal oxide which is loaded with acid radical ions on the surface and has the acidity of over 100 percent of sulfuric acid.
In a preferred embodiment, the metal oxide solid super acid is a sulfate supported metal oxide solid super acid.
In a preferred embodiment, the sulfate supported metal oxide solid super acid is selected from the group consisting of SO42-/ZrO2、SO42-/Fe2O3、SO42-/TiO2、SO42-/Al2O3、SO42-/SnO2、SO42-/Al2O3-ZrO2、SO42-/TiO2-ZrO2One or more combinations thereof.
In a more preferred embodiment, the sulfate supported metal oxide solid super acid is selected from SO42-/ZrO2、SO42-/Al2O3-ZrO2、SO42-/TiO2-ZrO2One or more combinations thereof.
In a more preferred embodiment, the solid acid is a lewis acid.
In a preferred embodiment, the mass fraction of the concentrated sulfuric acid is 98%.
In a preferred embodiment, the weight ratio of the waste silicone rubber powder, the concentrated sulfuric acid and the solid acid is 1: (0.02-0.05): (0.08-0.15).
In a more preferred embodiment, the weight ratio of the waste silicone rubber powder, the concentrated sulfuric acid and the solid acid is 1: 0.035: 0.12.
< step three >
In a preferred embodiment, the heating temperature of the pretreated waste silicone rubber powder in the third step is 140 to 200 ℃.
In a more preferred embodiment, the temperature for heating the waste silicone rubber powder pretreated in the third step is 170 ℃.
In a preferred embodiment, the vacuum condition in the third step is 0.08MPa or less.
In a more preferred embodiment, the vacuum condition in step three is 0.08 MPa.
At present, the method widely used in industry for recovering cyclosiloxane monomer by acid catalytic cracking of waste silicon rubber is a concentrated sulfuric acid cracking method, which has high cracking efficiency, but has the problems of strong corrosivity, high equipment replacement rate, difficult treatment of cracking residue, serious pollution and the like. The acid catalytic cracking of the waste silicon rubber can also adopt a solid acid cracking method, the corrosivity is low, but the whole cyclic siloxane monomer recovery period is greatly prolonged compared with that of concentrated sulfuric acid cracking due to insufficient reaction contact surface. The inventor creatively combines concentrated sulfuric acid and a solid acid composite catalyst, but how to improve the catalytic cracking efficiency while reducing the corrosion to equipment is a big problem which the inventor has to solve.
The inventor unexpectedly discovers that when the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the solid acid is 1: (0.02-0.05): (0.08-0.15), the mass fraction of concentrated sulfuric acid is 98%, the solid acid is Lewis acid, and the catalytic cracking efficiency can be improved while the corrosion of the system to equipment is reduced by matching with the specific raw material particle size and the preparation process. The inventor conjectures the possible reason that under the condition of specific raw material particle size and preparation process, a certain proportion of concentrated sulfuric acid and active centers in Lewis acid attack cyclic siloxane with larger molar mass together to promote the generation of linear macromolecular siloxane in a system; meanwhile, a certain amount of concentrated sulfuric acid can attack the Si-O-Si bond of the linear macromolecular siloxane again, and the linear Si-O-Si in the system is promoted to be broken and degraded by cooperating with the attack of Lewis acid on oxygen atoms with large electronegativity, and cyclic siloxane monomers with low molar mass are generated by rearrangement. However, when the proportion of concentrated sulfuric acid in the system is too small or the mass fraction is too small, the acid catalyst in the system is not enough to attack a large amount of cyclic siloxane with large molar mass, the reaction recovery rate is low, and the reaction period is long; when the proportion of concentrated sulfuric acid in the system is too high, the corrosion to equipment is obviously increased, the reaction recovery rate is low, and the recovery is unstable.
The present invention will now be described in detail by way of examples, and the starting materials used are commercially available unless otherwise specified.
Examples
Example 1
The embodiment 1 of the invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 98%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.035: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step two at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 65% relative to the mass of the waste silicon rubber.
Example 2
The embodiment 2 of the invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 98%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.02: 0.08;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step (II) at 140 ℃ until the material is liquefied, stirring and mixing for 5min, reacting for 3h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 45% relative to the mass of the waste silicon rubber.
Example 3
The embodiment 3 of the invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 98%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.05: 0.15;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step (II) at 200 ℃ until the material is liquefied, stirring and mixing for 10min, reacting for 5h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 65% relative to the mass of the waste silicon rubber.
Example 4
Embodiment 4 of the present invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, comprising the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous aluminum chloride and 98% concentrated sulfuric acid by mass percent, mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous aluminum chloride is 1: 0.035: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step two at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 62% relative to the mass of the waste silicon rubber.
Example 5
Embodiment 5 of the present invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, comprising the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, and adding sulfate radical-loaded metal oxide solid super acid SO42-/ZrO2Mixing and stirring the waste silicon rubber powder and concentrated sulfuric acid with the mass fraction of 98 percent to obtain pretreated waste silicon rubber powder; the waste silicon rubber powder, concentrated sulfuric acid and sulfate radical loaded metal oxide solid super acidSO42-/ZrO2The weight ratio of (1): 0.035: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step two at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 52% relative to the mass of the waste silicon rubber.
Example 6
Embodiment 6 of the present invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, comprising the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, and adding sulfate radical-loaded metal oxide solid super acid SO42-/Al2O3-ZrO2Mixing and stirring the waste silicon rubber powder and concentrated sulfuric acid with the mass fraction of 98 percent to obtain pretreated waste silicon rubber powder; the waste silicon rubber powder, concentrated sulfuric acid and sulfate radical loaded metal oxide solid super acid SO42-/Al2O3-ZrO2The weight ratio of (1): 0.035: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step two at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 58% relative to the mass of the waste silicon rubber.
Example 7
Embodiment 7 of the present invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, comprising the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, and adding sulfate radical-loaded metal oxide solid super acid SO42-/TiO2-ZrO2Mixing and stirring the waste silicon rubber powder and concentrated sulfuric acid with the mass fraction of 98 percent to obtain pretreated waste silicon rubber powder; the above-mentionedWaste silicon rubber powder, concentrated sulfuric acid and sulfate radical loaded metal oxide solid super acid SO42-/TiO2-ZrO2The weight ratio of (1): 0.035: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step two at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 60% relative to the mass of the waste silicon rubber.
Comparative example 1
The invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 3 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 98%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.035: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step two at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 33% relative to the mass of the waste silicon rubber.
Comparative example 2
The invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 85%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.035: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step two at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 36% relative to the mass of the waste silicon rubber.
Comparative example 3
The invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 98%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.01: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step (II) at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 30% relative to the mass of the waste silicon rubber.
Comparative example 4
The invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 98%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.06: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step two at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 42% relative to the mass of the waste silicon rubber.
Comparative example 5
The invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 98%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.035: 0.07;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step two at 170 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 26% relative to the mass of the waste silicon rubber.
Comparative example 6
The invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 98%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.035: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step (II) at 120 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer accounting for 31% of the mass of the waste silicon rubber.
Comparative example 7
The invention provides a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber, which comprises the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder with the particle size of 2 mm;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding anhydrous zinc chloride and concentrated sulfuric acid with the mass fraction of 98%, and mixing and stirring to obtain pretreated waste silicon rubber powder; the weight ratio of the waste silicon rubber powder to the concentrated sulfuric acid to the anhydrous zinc chloride is 1: 0.035: 0.12;
step three: and (3) heating the pretreated waste silicon rubber powder obtained in the step (II) at 220 ℃ until the material is liquefied, stirring and mixing for 7.5min, reacting for 4h under the vacuum condition of 0.08MPa, and collecting to obtain a cyclosiloxane monomer with the mass of 40% relative to the mass of the waste silicon rubber.
The combination of the above experimental results shows that: according to the method, the waste silicon rubber is cracked by adopting the solid acid and concentrated sulfuric acid composite catalyst in a specific ratio, the catalytic cracking efficiency is high, and the cyclosiloxane monomer accounting for 45-65% of the mass of the waste silicon rubber can be recovered. Meanwhile, the corrosion of the cracking process to equipment can be reduced, the calcium sulfate and the residual sulfuric acid generated in the cracking slag are also greatly reduced, the subsequent treatment and the further recycling of the cracking slag are facilitated, and the industrial application prospect is strong.
The foregoing examples are merely illustrative and serve to explain some of the features of the method of the present invention. The appended claims are intended to claim as broad a scope as is contemplated, and the examples presented herein are merely illustrative of selected implementations in accordance with all possible combinations of examples. Accordingly, it is applicants' intention that the appended claims are not to be limited by the choice of examples illustrating features of the invention. The invention is not limited to the embodiments described above, but rather, many modifications and variations may be made by one skilled in the art without departing from the scope of the invention.
Claims (10)
1. A method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber is characterized by comprising the following steps:
the method comprises the following steps: cleaning, drying and crushing waste silicon rubber to obtain waste silicon rubber powder;
step two: putting the waste silicon rubber powder obtained in the step one into a reactor, adding solid acid and concentrated sulfuric acid, mixing and stirring to obtain pretreated waste silicon rubber powder;
step three: and (3) heating the pretreated waste silicone rubber powder obtained in the step two until the material is liquefied, stirring and mixing for 5-10 min, reacting for 3-5 h under a vacuum condition, and collecting to obtain a cyclosiloxane monomer.
2. The method for recovering cyclosiloxane monomer through catalytic cracking of waste silicone rubber according to claim 1, wherein the particle size of the waste silicone rubber powder is less than 2 mm.
3. The method for recovering cyclosiloxane monomer through catalytic cracking of waste silicone rubber according to claim 1, wherein the solid acid is Lewis acid and/or metal oxide solid super acid.
4. The method for recovering cyclosiloxane monomer through catalytic cracking of waste silicone rubber according to claim 3, wherein the Lewis acid is selected from one or more of zinc chloride, aluminum chloride, zirconium chloride, titanium chloride and silicon chloride.
5. The method for recovering cyclosiloxane monomer through catalytic cracking of waste silicone rubber according to claim 3 or 4, wherein the metal oxide solid super acid is a sulfate radical supported metal oxide solid super acid.
6. The method for recovering cyclosiloxane monomer through catalytic cracking of waste silicone rubber according to claim 5, wherein the sulfate radical supported metal oxide solid super acid is selected from SO42-/ZrO2、SO42-/Fe2O3、SO42-/TiO2、SO42-/Al2O3、SO42-/SnO2、SO42-/Al2O3-ZrO2、SO42-/TiO2-ZrO2One or more combinations thereof.
7. The method for recovering cyclosiloxane monomer through catalytic cracking of waste silicone rubber according to claim 1, wherein the mass fraction of the concentrated sulfuric acid is 98%.
8. The method for recovering cyclosiloxane monomer through catalytic cracking of waste silicone rubber according to claim 1, wherein the weight ratio of the waste silicone rubber powder, concentrated sulfuric acid and solid acid is 1: (0.02-0.05): (0.08-0.15).
9. The method for recovering cyclosiloxane monomer through catalytic cracking of waste silicone rubber according to claim 1, wherein the heating temperature of the pretreated waste silicone rubber powder in the third step is 140-200 ℃.
10. The method for recovering cyclosiloxane monomer through catalytic cracking of waste silicone rubber according to claim 1, wherein vacuum condition in the third step is below 0.08 MPa.
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| CN114031636A (en) * | 2021-11-12 | 2022-02-11 | 福建师范大学 | Mechanical force chemical grinding assisted waste silicon rubber thermal cracking recovery method |
| CN114516977A (en) * | 2022-03-07 | 2022-05-20 | 广东省科学院资源利用与稀土开发研究所 | Method for recovering cyclosiloxane monomer by cracking waste silicone rubber under catalysis of rare earth |
| WO2023222749A1 (en) * | 2022-05-19 | 2023-11-23 | Elkem Silicones France Sas | Depolymerization of silicone to obtain organochlorosilane |
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